I believe that's a laser. But you would have to make sure somehow that it wouldn't reflect off of any particles en route. Which would likely be impossible... un

I believe that's a laser. But you would have to make sure somehow that it wouldn't reflect off of any particles en route. Which would likely be impossible... unless the wavelength was very, very long, I think. Also, the laser would spread out, but it would still be mostly in one direction.